Alignment unit for sheet material

ABSTRACT

The invention relates to an alignment unit for sheet material ( 1 ) which is upstream of the conveyor plane ( 9 ) for the sheet material ( 1 ). Feed of the sheet material ( 1 ) takes place via driven surfaces ( 33 ) which touch at least one side of the sheet material ( 1 ). The alignment unit ( 8 ) holds rotation elements ( 25, 38 ) which grip the sheet material ( 1 ) and which correct the offset of the sheet material ( 1 ) with reference to the direction ( 22 ) in which it is running. Of them, at least two rotation elements ( 25 ) which lie in one plane can be moved to the remaining rotation elements ( 38 ).

[0001] The invention relates to an alignment unit for sheet material, as can be used for example in the feed of stock to sheet-processing printing presses in order to exactly align the material to be printed.

[0002] DE 44 16 564 A1 discloses a sheet alignment device. This device for alignment of a sheet moving along an essentially flat transport path enables alignment of a moving sheet in a plurality of orthogonal directions, for example transversely to the transport path, in the direction of the transport path, and to eliminate skewed positions. The device has a first roller arrangement with a first pressure roller which is supported such that it can turn around one axis which lies in a plane which extends parallel to the plane of the transport path and runs essentially at a right angle to the direction of sheet transport along the transport path. A second roller arrangement has a second pressure roller which is supported such that it can turn around one axis which lies in a plane which extends parallel to the plane of the transport path and runs essentially at a right angle to the direction of sheet transport along the transport path. There is a third roller arrangement which has a third pressure roller which is supported such that it can turn around one axis which lies in a plane which extends parallel to the plane of the transport path and runs essentially at a right angle to the direction of sheet transport along the transport path. The third roller arrangement which can turn around one axis which lies in a plane which extends parallel to the plane of the transport path and runs essentially at a right angle to the direction of sheet transport along the transport path can be moved along its axis of rotation in the direction which runs transversely to the transport path. Finally, there is a control means which is dynamically connected to the first and the second and the third roller arrangement and selectively controls the rotation of the first and second roller arrangement in order to align the front edge of a sheet moving in the direction of sheet transport along the transport path into the position which is at a right angle to the direction of sheet transport. The control means furthermore controls the rotation and the transverse motion of the third roller arrangement in order to align the moving sheet in the direction which runs transversely to the direction of sheet transport and in the direction in which the sheet is moving along the transport path.

[0003] The sheet alignment device known from DE 44 16 564 A1 enables the required alignment accuracies to be satisfied only to a limited degree. To achieve the required alignment accuracies, extensive modification of the sheet alignment device of the prior art is necessary, which modification does not seem economical.

[0004] In sheet-processing printing presses which work using the offset principle, the sheets are conveyed on the feed table in a ragged arrangement before they are aligned on the side and pull-type lay marks which are provided in the plane of the feed table. After completed alignment of the sheet material it is transferred in the aligned state to a pre-gripper which accelerates the sheet material to the press speed and transfers it to a sheet-guiding cylinder which is located downstream of the pre-gripper means.

[0005] This approach is subject to very high control engineering and mechanical complexity.

[0006] In view of the defects of the approaches known from the prior art, the object of the invention is to carry out alignment of sheet material such that unprinted sheet material, already printed sheet material or sheet material with pictures printed on it in some other way is neither influenced by the components which undertake alignment, in its aligned position, nor is the upper side damaged or in some other way adversely affected.

[0007] As claimed in the invention this object is achieved by the features of claim 1.

[0008] The advantages which can be achieved with the approach as claimed in the invention are mainly that by making the rotation elements which grip the sheet material in the alignment unit as movable rotation elements, the alignment unit changes of the coefficient of friction on the surfaces of the counterpressure rollers by the developing wear or relaxing normal force are compensated, as are changes of the coefficient of friction of the segmented rollers which are provided above the sheet conveyor plane within the alignment units [sic]. The normal force necessary to produce the feed force between the peripheral surfaces of the segmented rollers and counterpressure rollers which interwork with one another can be produced for example by elastic spring elements. The reset of the counterpressure rollers after completed displacement transversely to the sheet conveyor direction within the alignment unit can be set back again into its original position after correction of the location of the stock to be aligned relative to the direction in which it is running with an actuator, whether mechanical cam disks or electrical or pneumatic actuators.

[0009] In an advantageous embodiment of the idea underlying the invention, the feed force acting on the sheet material can be produced by adjustment of a pair of rotation elements which lies in one plane, whether driven segmented rollers or the counterpressure rollers, to the other pair of rotation elements at the time. Advantageously energy storage mechanisms, for example spring elements, can be used for this purpose.

[0010] The adjustment of the normal force on the sheet material can be applied both by applying the normal force to the segmented rollers located in the plane above the sheet conveyor plane and also on the counterpressure rollers located underneath the sheet conveyor plane.

[0011] Advantageously the rotation elements which touch the sheet material are made as segmented rollers, with a peripheral development which describes roughly a three quarters circle.

[0012] In another advantageous embodiment of the idea underlying the invention, bodies of revolution which are made as segmented rollers, viewed in the direction in which the sheets are running, are arranged in successive pairs or groups. The segmented rollers which are each held in twos spaced apart from one another in the plane which lies above the sheet conveyor plane are driven via drives. The drives of the segmented rollers 25 are positioned in a first orientation and in a second orientation with respect to the direction in which the sheets are running. The first orientation is characterized in that the driven axles of the drives are perpendicular to the direction in which the sheets are running, while the second orientation is characterized in that the driven axle of the drive runs parallel to the direction in which the sheets are running.

[0013] In one embodiment of the idea underlying the invention, the counterpressure rollers located underneath the conveyor plane of the sheet material can be held stationary on axles, while the bodies of revolution which are made interacting with them as segmented rollers execute displacement relative to the counterpressure rollers which are held stationary. In this embodiment the width of the counterpressure rollers which are supported stationary underneath the conveyor plane of the sheet material exceeds that of the segmented rollers in the plane above the conveyor plane of the sheet material. In another embodiment of the subject matter of the invention the counterpressure rollers can be made as a common unit which can be moved relative to the segmented rollers. The width of the peripheral surfaces of the counterpressure rollers thus corresponds to the width of the segmented rollers which are located in the plane in pairs above the conveyor plane of the sheet material. The alignment unit proposed as claimed in the invention can be used on a feeder to feed sheet material to a machine which processes this material, for example. Printing presses equipped with the alignment unit proposed as claimed in the invention for processing of sheet material are characterized by the fact that staggered stacking and the concomitant danger of interruption of sheet feed in case of problems in stacking are eliminated.

[0014] The invention is detailed below using drawings.

[0015]FIG. 1 shows the developing position deviation of a printed image relative to the surface of a sheet,

[0016]FIG. 2 shows the position offset of the printed image to be applied to the sheet material, i.e. the offset characterized by a rotary offset,

[0017]FIG. 3 shows the offset of the image which has been printed on the bottom and top of the sheet material,

[0018]FIG. 4 schematically shows a side view of the sheet feed area into a sheet-processing machine,

[0019]FIG. 5 shows a plan view of the alignment components, the sensors and drives of the rotation elements which align the sheet material relative to the direction in which the sheets run,

[0020]FIG. 6 shows the rotation elements which are made as claimed in the invention as segmented rollers above the conveyor plane of the stock, in the active and inactive position,

[0021]FIGS. 7, 8 and 9 show drive activations of the rotation elements which are made as segmented rollers and which are located above the sheet conveyor plane, which activations are necessary for alignment of sheet material relative to the direction 22 in which the sheets are running,

[0022]FIG. 10 shows the segmented rollers which can be moved jointly relative to the counterpressure rollers which are supported stationary on individual axles in the displacement direction and

[0023]FIG. 11 shows the counterpressure rollers which can likewise be moved synchronously to the displacement of the segmented rollers.

[0024]FIG. 1 shows sheet material, for example a printed sheet 1, which is oriented at a right angle. The printed sheet 1 contains on its surface a printed image 2 which is surrounded by a frame-like edge 3. The deviations Δx and Δy which are marked within the printed surface 2 and the frame 3 designate the position errors in the x and y direction which can be adjusted when printing the image 2 onto the surface of the sheet. The deviations labeled with reference numbers 4 and 5 are position deviations, conversely in the representation as shown in FIG. 2 angle deviations of the printed image 2 are shown with reference to its position on the printed sheet 1.

[0025] In FIG. 2 the developing angular errors Δφ are labeled with reference number 6. The printed image 2 can be printed in the indicated positions onto the surface of the stock material 1, its being conveyed with its conveyor edge 23 forward in the direction in which the sheet is running.

[0026]FIG. 3 shows in a schematic view the turning register, and the offsets which develop between the printed images 2 on the front and back of the sheet material 1 can be characterized with reference number 7. These offsets are labeled with reference number 7 and with Δx and Δy in FIG. 3. The turning register plays an important part especially in translucent types of paper and when printing booklets.

[0027]FIG. 4 shows in a schematic side view the sheet alignment-conveyor belt interface.

[0028] An alignment unit 8 is connected upstream of a transport belt 10 which runs around a feed roller 11 and a control roller 12; on the surface of the belt the sheet material is held in the conveyor plane 9. After passing the alignment unit 8 which will be described in greater detail below, the aligned sheet material 1 travels onto the surface of the transport belt 10 into the conveyor plane 9. After passing the feed roller 1 the sheet material 1 is captured by an adjustment flap or adjustment lip which can be moved in the adjustment direction 13.

[0029] The adjustment lip or adjustment flap can be a plastic component which can be moved from the adjusted position 13.1 into the stopped position 13.2; this is shown here only schematically in solid or broken lines. By means of the adjustment flap or the adjustment lip 13 pressing of the sheet material 1 onto the surface of the transport belt 10 in the aligned state of the sheet material 1 follows. After passing the pressure element the sheet which is held on the surface of the transport belt 10 passes a charging unit 14. In the charging unit 14, inside a hood-shaped cover there is an electrode 15 which provides for static charging of the sheet material 1 and thus for its adhesion to the surface of the transport belt 10.

[0030] A front edge sensor 17 follows the charging unit 14 which is shown only schematically in FIG. 4. This sensor consists of a radiation source 18 which is located underneath the sheet conveyor plane 9 and to which a lens arrangement 19 is series connected. The radiation field 20 proceeding from the lens arrangement 19 penetrates the sheet conveyor plane 9 and is incident on a diaphragm arrangement which is located above the conveyor path of the sheet material 1 in the conveyor plane 9. The diaphragm arrangement precedes a receiver 21 which registers the presence of the front edge 23 of the sheet material 1.

[0031]FIG. 5 shows in a plan view the alignment unit 8 with its components which are shown schematically here.

[0032] The alignment unit 8 is reached by the sheet material 1 which is conveyed in the conveyor direction 22. The front edge 23 of the sheet material 1 is offset with respect to the direction 22 in which the sheet material is running, by which the side edges 24 of the sheet material 1 begin to run skewed. As soon as the front edge 23 of the sheet which is in the skewed position with respect to the running direction 22 runs over a photoelectric barrier 26, the drives 27, labeled M1 and M2, which drive rotation elements 25 via individual axles 32, are accelerated to the feed rate. This triggering of the drives 27 and M1 or M2 which is initiated via the photoelectric barrier 26 ensures that each copy of the sheet material 1 comes into contact with identical peripheral segments of the rotation elements 25 which can be made for example as segmented rollers. Any developing differences in the feed motion which could be attributed to the dimensional and shape tolerances of the two rotation elements 25, driven by the drives M1 and M2, thus occur in the same way for each copy of the sheet material 1 and can be easily calibrated out.

[0033] After the rotation elements 25 are set into rotation by passing the first photoelectric barrier 26, the sheet is transported with the feed rate over another sensor unit 30.1 which follows the first photoelectric barrier 26. As soon as the first of the two sensors 30.1 has detected the front edge 23 of the sheet material 1, a counter unit begins to count the motor steps. The counting process is ended when the second sensor of the sensor pair 30.1 operates.

[0034] The counter state which has been determined in this way is used to determine a correction value which as additional feed on the segmented roller drive which was started last, i.e. either the drive 27 which is labeled M1, or the one which is labeled M2 [sic].

[0035] In this way the corresponding body 25 of revolution which is made for example as a segmented roller is moved with an increased feed rate until the stipulated path difference is completely equalized. At the end of this correction process the front edge 23 of the sheet is oriented exactly perpendicularly to the direction 22 in which the sheet is running.

[0036] After completed correction, the sheet material 1 in the direction 22 in which it is running is continuously transferred from the first pair of bodies 25 of revolution to the pair of bodies 25 of revolution following it, and they are accommodated on a common axle 31. At this point the segmented roller pair 25 which is driven via the drives 27 or M1, M2 is turned off and moves into a neutral position.

[0037] The sheet which is now correctly aligned with respect to its angular position now runs onto a sensor array 30 in which the position of the side edges 24 of the sheet material 1 is measured. The change in position for the drive 27 which is labeled M4 and which has a drive shaft which extends parallel to the direction 22 in which the sheet is running is determined from the established measured value. By means of this drive 27 which is held in a second orientation 29, a correction change of the sheet material 1 parallel to the direction 22 in which it is running takes place (compare FIG. 7).

[0038] Afterwards, the sheet 1 which is aligned in this way in its angular position and its lateral position accordingly to the transport belt 10 runs underneath an adjustment flap or adjustment lip which has been swiveled in the adjustment position onto the transport belt 10 in order to run into the downstream printing unit in the correctly aligned position.

[0039]FIG. 6 shows one embodiment of the rotation element 25 which is located above the conveyor plane 9 of the sheet material 1 and which is held in the alignment unit 8.

[0040] The rotation elements 25 in one preferred embodiment can be made as segmented rollers which have a peripheral surface 33 which is characterized by an interruption. The segmented rollers 25 rotate in direction 34, characterized by the arrow, and describe roughly a three quarters circle with reference to their axes of rotation. Underneath the respective segmented rollers 25, a roller which supports the sheet material 1 is shown, here only schematically. The segmented rollers 25 which are used as bodies of revolution are show in the neutral position in the left part of FIG. 6, while in the right part of FIG. 6 with their peripheral surface they grip a copy of the sheet material 1 which is conveyed in the direction 22 in which the sheet is running and transport it according to the direction 34 of rotation.

[0041]FIGS. 7, 8 and 9 in sequence show the correction of the angular position and the correction of the side position of the sheet material 1 when passing the alignment unit 8.

[0042] In the position of the sheet material 1 shown in FIG. 7, its front edge 23 has already reached the last sensor of the sensor pair 30.1, so that now the drive 27 of the segmented roller 25 labeled M1 can be activated in order to equalize the angular position of the sheet material 1 with respect to the running direction 22. It should be mentioned that in contrast to the drives M3 and M4 which are connected to one another by a continuous drive shaft 31, the segmented rollers 25 which are connected to drives M1 and M2 are each driven via individual shafts 32.

[0043] After correction of the angular position of the sheet material 1, as shown in FIG. 7, the sheet material 1 undergoes correction of its side position.

[0044] After measuring the location of the side edges 24 of the sheet material 1 by the sensor filters 30 which are accommodated in the area of the side edges of the conveyor path 9 of the sheet material, the measured value determined by the side edge sensors 30 is used to compute the position change which is relayed to the stepping motor 27, labeled M4, which is positioned in the second orientation 29, so that it adjusts the side edges 24 of the sheet material 1 to the arrow position labeled with reference number 37. In the state shown in FIG. 8, the segmented rollers 25 which are driven via the individual drives 27, labeled M1 and M2, are turned off and moved into their neutral position. They remain there until the arrival of the next copy of the sheet material 1 which is to be aligned with reference to its angular position and to its side position.

[0045] In the state of the alignment unit shown in FIG. 9, the sheet material 1 which has been aligned in its angular position and its side position is gripped on its front edge 23 by an adjusted adjustment flap or adjustment lip which is in the adjustment position 13.1. In this way the aligned sheet material 1 is pressed onto the surface of the turning transport belt 10, the side edges 24 of the sheet material 1 corresponding exactly to the position of the indicator 37. The aligned sheet material 1 is now transported in the conveyor plane 9 by the rotating transport belt 10 which supports the sheet material 1 and to which the sheet material 1 is adjusted by the adjustment element. After the sheet material 1 has been transferred to the transport belt 10 which runs around the feed roller 11 and the control roller 12, the correction process is ended; now the second segmented roller pair 25, driven via the individual drive 27, labeled M3, is also moved into its neutral position and is thus ready for correction of the next copy of the sheet material 1. By making the bodies 25 of revolution as segmented rollers, feed of the sheet material 1 over a limited path length can take place without an operating process on the drive rollers or counterpressure rollers 38, compare FIG. 10, 11, being necessary. The limited path length by which the sheet material 1 is transported is defined by the development of the peripheral surface 33 of the segmented rollers 25. Two segmented roller pairs at time are held in the alignment unit 8, as shown in FIGS. 7, 8 and 9. The two segmented rollers 25 of the first pair can be triggered via the stepping motors M1 and M2 each separately in the feed direction, while the second segmented roller pair 25 is coupled via a common shaft 31. The latter can be moved in the feed direction or into the axial direction by means of the stepping motors 27, labeled M3 and M4.

[0046] In FIG. 10 the counterpressure rollers are assigned to the bodies of revolution made as segmented rollers in an alignment unit.

[0047]FIG. 10 shows that the segmented rollers 25 which have peripheral surfaces 33, held for example on a common axle 31, can be pushed in the direction of the double arrow (compare alignment process as shown in FIG. 8). Underneath the conveyor plane which is defined by the peripheral surfaces of the counterpressure bodies 38 and the segmented roller 25 the counterpressure bodies are held on individual shafts 44 and have a width 39 which, compared to the width of the peripheral surfaces 33 of the segmented rollers 25, is much larger. The individual axles 44 on which the counterpressure bodies are held can be for example spring-loaded in order to produce a normal force which causes feed between the peripheral surfaces of the counterpressure bodies and the peripheral surfaces 33 of the segmented rollers 25. The alignment of the sheet material 1 with the configuration shown schematically in FIG. 10 makes it possible to set the frictional force between the segmented rollers 25 and the sheet material 1 greater than the frictional force which prevails between the bodies 38 of revolution and the stock, so that there is no slip between the segmented rollers 25 and the stock.

[0048] It follows from the embodiment shown in FIG. 11 that the bodies of revolution made as segmented rollers, held for example on a common axle 31, can be moved there in the direction of the double arrow. If the counterpressure bodies held for example on a common axle 43 are made as a movable unit in the axial direction, the alignment unit 8 is resistant to changes in the coefficient of friction on the peripheral surfaces 45 of the counterpressure bodies 38 and resistant and invulnerable to changes in the coefficient of friction on the peripheral surfaces 33 of the segmented rollers 25. Developing changes in these coefficients of friction can be equalized by matching to the normal force. The normal force can be applied to the common axles 31 and 43 in the form of spring elements which can be adjusted to it; but other pretensioning elements can also be used, for example, tensioning screws or tension rods or the like. Resetting of the counterpressure bodies 38 which are held as a movable unit on the common axle 43 into their initial position can be done after a side correction with reference to the direction 22 in which the sheet material 1 is running with a suitable actuating means, for example mechanical cam disks, electrical or pneumatic actuators.

[0049] With this approach, by means of specific adjustment of the coefficient of friction, care can be taken that by means of the peripheral surfaces 33 of the segmented rollers 25, which surfaces can be adjusted to the surface of the sheet material 1, the generated frictional force is enough for alignment, and can be set higher than that frictional force which prevails between the peripheral surfaces 45 of the counterpressure bodies 38 and the bottom of the sheet material 1. This guarantees that in the alignment process underway no marks or traces remain on the pages of sheet material 1, whether unprinted material, material printed on one side, or material already printed on both sides. Furthermore, it is ensured that the sheet material 1 is not adversely affected in its aligned position and can run exactly positioned in it into the sheet-processing machine, such as for example a printing press or a digital printing press.

REFERENCE NUMBER LIST

[0050]1 sheet material

[0051]2 printed image

[0052]3 frame

[0053]4 position error, y direction

[0054]5 position error, x direction

[0055]6 twist error

[0056]7 offset, printed sheet front and back (1)

[0057]8 alignment unit

[0058]9 conveyor plane

[0059]10 transport belt

[0060]11 feed roller

[0061]12 control roller

[0062]13 adjustment direction on adjustment flap

[0063]13.1 first position

[0064]13.2 second position

[0065]14 charging unit

[0066]15 electrode

[0067]16 support

[0068]17 front edge sensor

[0069]18 radiation source

[0070]19 lens

[0071]20 radiation field

[0072]21 radiation receiver

[0073]22 direction in which sheet material is running

[0074]23 front edge

[0075]24 side edge

[0076]25 segmented rollers

[0077]26 photoelectric barrier

[0078]27 drives, segmented rollers

[0079]28 first orientation, drive

[0080]29 second orientation, drive

[0081]30 sensor array (x sensor)

[0082]30.1 sensor pair

[0083]31 continuous shaft

[0084]32 individual shaft

[0085]33 periphery of the segmented roller

[0086]34 direction of rotation

[0087]35 segmented roller, active position

[0088]36 segmented roller, inactive position

[0089]37 indicator, side position

[0090]38 counterpressure element

[0091]39 width

[0092]40 axis

[0093]41 displacement motion

[0094]42 common axis

[0095]43 individual axis

[0096]44 peripheral surface 

1. Alignment unit for sheet material (1) which is upstream of the conveyor plane (9) for the sheet material (1) and feed of the sheet material (1) takes place via driven surfaces (33) which touch at least one side of the sheet material (1), wherein the alignment unit (8) holds rotation elements (25, 38) which grip the sheet material (1) and which correct the offset of the sheet material (1) with reference to its conveyor direction (22), of which at least two rotation elements (25) which lie in one plane can be moved to the remaining rotation elements (38).
 2. Alignment unit as claimed in claim 1, wherein the feed acting on the sheet material (1) is produced by adjusting one pair of rotation elements (25, 38) which lies in one plane to the other pair of rotation elements (25, 38) at the time which lies in another plane.
 3. Alignment unit as claimed in claim 2, wherein a normal force on the sheet material (1) takes place by applying a spring force to a pair of rotation elements (25, 38) which lies in one plane.
 4. Alignment unit as claimed in claim 1, wherein the rotation elements (25) which touch the sheet material (1) are made as segmented rollers.
 5. Alignment unit as claimed in claim 1, wherein the segmented rollers (25) viewed in the direction 22 in which the sheet is running are arranged in successive pairs.
 6. Alignment unit as claimed in claim 5, wherein the segmented rollers (25) are driven by drives (27).
 7. Alignment unit as claimed in claim 6, wherein the drives (27) of the segmented rollers (25) are positioned in the first orientation (28) and in the second orientation (29) with respect to the direction (22) in which the sheet material (1) is running.
 8. Alignment unit as claimed in claim 1, wherein the counterpressure elements (38) which are provided underneath the conveyor plane (9) are held stationary on axles (44), while the segmented rollers (25) execute a displacement (42) to them.
 9. Alignment unit as claimed in claim 1, wherein the width (39) of the counterpressure elements (38) which are supported stationary exceeds that of the segmented rollers (25).
 10. Alignment unit as claimed in claim 1, wherein the counterpressure elements (38) are made as a common unit (43) which can be moved relative to the segmented rollers (25).
 11. Alignment unit as claimed in claim 10, wherein the width of the peripheral surfaces (45) of the counterpressure elements (38) corresponds to the width of the segmented rollers (25).
 12. Feeder for feed of sheet material (1), with an alignment unit (8) which is upstream of the conveyor plane (9) for the sheet material (1) and feed of the sheet material (1) takes place via driven surfaces (33) which touch at least one side of the sheet material (1), wherein the alignment unit (8) holds rotation elements (25, 38) which grip the sheet material (1) and which correct the offset of the sheet material (1) with reference to the direction (22) in which it is running, of which at least two rotation elements (25) which lie in one plane can be moved to the remaining rotation elements (38).
 13. Printing press with an alignment unit (8) for sheet material (1), which is upstream of the conveyor plane (9) for the sheet material (1) and feed of the sheet material (1) takes place via driven surfaces (33) which touch at least one side of the sheet material (1), wherein the alignment unit (8) holds rotation elements (25, 38) which grip the sheet material (1) and which correct the offset of the sheet material (1) with reference to its conveyor direction (22), of which at least two rotation elements (25) which lie in one plane can be moved to the remaining rotation elements (38). 